Many readers have offered support for a lawsuit filed by former U.S. servicemen and others claiming they were affected by radiation during "Operation Tomodachi," a U.S. Armed Forces operation to assist Japan in the wake of the March 2011 Great East Japan Earthquake and tsunami. These readers reacted to last week's installment of the Japan Political Pulse column that mentioned former Prime Minister Junichiro Koizumi's activities to support the lawsuit.

It has not yet been proven if there is a causal relationship between so-called second-hand exposure to radiation and health problems. Critics say emotional support for those who claim their health was affected by indirect exposure to radiation without scientific proof is irresponsible. Emotional support is important but objective facts should also be clarified.

Eight former U.S. soldiers who participated in Operation Tomodachi (friend) launched the lawsuit in California in December 2012. The number of plaintiffs has since surpassed 450.

In March 2011, 16 U.S. military vessels engaged in the operation, including the aircraft carrier Ronald Reagan, were exposed to radiation off Fukushima Prefecture. These vessels and the servicemen aboard them were engaged in the operation amid a radioactive plume from the tsunami-hit Fukushima No. 1 Nuclear Power Plant.

According to the lawsuit, the plaintiffs have been suffering from such illnesses as leukemia, testis cancer, colon bleeding, ringing in their ears and a decline in eyesight since they returned home after participating in the operation.

They are suing Tokyo Electric Power Co., the operator of the nuclear plant, Toshiba Corp., Hitachi Ltd., and other Japanese and U.S. atomic power station manufacturers, demanding that a 1 billion dollar (some 100 billion yen) fund be set up to help the plaintiffs receive medical examinations and treatment.

The plaintiffs are hoping that their suit will be tried in the United States, while TEPCO is demanding that the case be heard in Japan.

In June 2015, TEPCO's appeal over the jurisdiction over the trial was accepted, and a state appeal court is deliberating on the matter.

The aforementioned development of the case is based on interviews with former Prime Minister Koizumi, who met with some of the plaintiffs, and officials at the Foreign Ministry and the Agency for Natural Resources and Energy. TEPCO declined to comment on the matter on the grounds that the trial is ongoing.

Under the civil discovery system established by U.S. law, those involved in civil lawsuits can be forced to disclose evidence. Those who refuse to comply could be imprisoned or slapped with a huge fine for contempt of court. Critics say TEPCO demands that the suit be tried in Japan for this reason.

One cannot help but wonder what the company does not want to be exposed. There is a possibility that documents carrying information on the cause of the nuclear plant accident, TEPCO's initial response to the disaster and observed data on aerial radiation levels -- which is different from what the utility has explained -- could be hidden. However, this is just a presumption without basis.

There is also an amicus curiae (court adviser) system, under which individuals or organizations appointed by courts provide information or express opinions on legal matters relating to individual court cases.

A former legislator has phoned the Mainichi Shimbun and raised questions about last week's installment of this column, which quoted a magazine article as saying that an adviser from the Japanese government stated that U.S. forces are responsible for servicemen's exposure to radiation while engaging in Operation Tomodachi.

Law360, a U.S.-based website specializing in information on legal affairs, lists the "Government of Japan" as the entity to which one of those who appeared in the oral proceeding on the lawsuit on Sept. 1 as court advisers belongs.

A senior official of the Agency for Natural Resources and Energy said, "The government isn't aware of such a figure." However, it would be no surprise if an adviser were to appear in court and develop a persuasive legal theory to pursue ways to evade legal responsibility on behalf of defendants.

Jonathan Woodson, assistant secretary of defense for health affairs who examined plaintiffs' assertions in 2014 at the request of U.S. Congress, stated there is no objective evidence that the plaintiffs' health hazard was caused by their exposure to radiation.

The March 13, 2016 issue of Stars and Stripes, a U.S. daily specializing in U.S. military information, covered Woodson's report along with a comment by Shinzo Kimura, associate professor of radiation hygiene at Dokkyo Medical University, that the possibility that the plaintiffs' symptoms were caused by their radiation exposure cannot be ruled out.

There is a long way to go before the causes of the plaintiffs' illnesses can be clarified. However, there is no denying that many people are suffering from illnesses after participating in Operation Tomodachi.

Donations to a fundraising drive launched by former Prime Minister Koizumi are accepted at the Tokyo-based Johnan Shinkin Bank. Koizumi will deliver a speech on the matter at a lecture meeting in Tokyo on the evening of Nov. 16. Those who want to listen to his speech are required to make reservations by calling the Japan Assembly for Nuclear Free Renewable Energy at 03-6262-3623. The admission fee of 10,000 yen per person will be fully donated to former U.S. soldiers who are suffering from illnesses. (By Takao Yamada, Special Senior Writer)